The present invention relates to a corrective intraocular lens, and more particularly to an artificial intraocular lens for use as an anterior chamber lens with an intact natural eye lens for correcting high myopia thereof, by insertion through an incision into the eye and implantation in the anterior chamber in spaced relation to the natural lens, in which the lens body or optic is provided with a pair of position fixation haptics which are differentially sized to aid safe insertion of the intraocular lens without damage to the natural lens during implantation.
For treatment of conditions such as high myopia of the natural eye lens, a known surgical procedure is to insert a corrective intraocular lens through an incision in the cornea of the eyeball, and implant such lens in the anterior chamber of the eye in spaced relation to the intact natural eye lens.
In these cases, since the natural lens remains intact, any foreign body introduced into the eye, such as an intraocular lens, must be introduced with the greatest of care by the surgical procedure used, so as to avoid any contact with the natural lens. This is because any contact with the sensitive natural lens by the foreign body could readily result in the natural lens becoming cataracted and/or in other injury to the natural lens of a serious, permanent nature.
Such injury is most likely to occur when maneuvering the intraocular lens during its insertion and seating in the eye, given the adverse conditions inherently involved, such as the confined space within the eye anteriorly of the intact natural lens, the fluid environment within the eye, the desire to keep the size of the corneal incision as small as possible to minimize trauma to the patient, the physical shape, size and make-up of the intraocular lens itself, and especially of its outwardly extending position fixation means, e.g. haptics, and the like.
In regard to the implantation of an anterior chamber intraocular lens for correcting the condition of a patient suffering from high myopia, for instance, the typical lens body or optic of the known type intraocular lens has a diameter of about 6 mm, and is provided with a pair of generally diametrically opposed and resiliently deflectable haptics of common shape and size, each terminating in a transverse edge portion having a typical length of about 6 mm and provided at its ends with a pair of similarly laterally spaced apart and outwardly projecting contact lobes for engaging the adjacent eye tissue in the anterior chamber, especially in the angle groove or "angle" defined between the scleral spur and the iris, by way of four point fixation technique.
These lobes may generally have a radius of about 0.125-0.25 mm, such that the outwardly projecting crests of the lobes are located about 0.125-0.25 mm beyond the remainder of the given transverse edge portion, and a like distance inwardly from the end edges of the transverse edge portion, making the length between the crests correspondingly about 5.75-5.5 mm for the typical 6 mm length transverse edge portion-containing haptic, these crests forming spaced-contact points engageable with the eye tissue.
As implanted, the intraocular lens is normally anteriorly of the iris and posteriorly of the scleral spur, but in any case is in spaced relation to the intact natural lens. It will be appreciated that, since the distance along the optical axis of the eye from the posterior surface of the cornea to the anterior surface of the natural lens is only about 3 mm, the intraocular lens must be inserted and implanted in the anterior chamber while maintaining it precisely parallel to the natural lens, so as to avoid twisting of the intraocular lens, which may cause it to touch the closely adjacent natural lens and result in serious, permanent damage thereto.
To accommodate such precise positioning of the intraocular lens, inasmuch as the angle groove normally has a diameter of about 12.5 mm, the overall longitudinal dimension of the known type intraocular lens from the transverse edge portion contact lobes of one haptic to those of the other haptic is usually about 13 mm.
The typical corneal incision is of a length just sufficient to accommodate the breadth of the optic during insertion, and in the normal case of an optic of about 6 mm diameter the incision length will likewise be about 6 mm. The location of the incision is usually somewhat anteriorly of the scleral spur and slightly closer to the optical axis of the eye than the scleral spur in terms of the spherical eyeball shape.
This means that, because of the anterior position of the incision relative to the angle groove, the linear distance between the line joining the end points of the incision and the most distant portion of the angle groove will be less than the above noted overall longitudinal dimension of about 13 mm from the transverse edge portion contact lobes of one haptic to the transverse edge portion contact lobes of the other haptic of the known type intraocular lens, such linear distance typically being only about 11 mm.
Hence, upon insertion in the usual case of the first or leading haptic through the incision, followed by the optic, and positioning of the leading haptic transverse edge portion contact lobes in seating engagement with the adjacent eye tissue portion in the angle groove most distant from the incision, the second or trailing haptic will remain outside of the eyeball, projecting outwardly from the incision a distance of about 1-2 mm.
To complete the insertion of the known type intraocular lens, substantial distortion thereof is necessary to squeeze all parts of the second or trailing haptic through the incision. Not only does the relatively unstable force transmission during this squeezing action potentially cause trauma to the eye tissue being placed under tensioning pressure, but it also raises the risk, as noted above, that the optic is caused to twist and as a result could touch the natural lens and cause permanent and serious injury thereto.
Considering the small size of the eyeball, and particularly of its interior portions as pertinent to the positioning of the known type intraocular lens, it becomes extremely important to maintain such lens out of contact with the natural lens, i.e. free from possible rotation and/or other substantial anterior or posterior displacement during insertion and seating of the intraocular lens.
It will be realized that the haptic transverse edge portions have a standard length dimension of relatively pronounced size, typically about 6 mm, so that the contact lobes thereon will be laterally spaced apart approximately a like distance, sufficient to provide stable positioning of the known type intraocular lens in the eye, especially at diametrically opposed portions of the angle groove. As a consequence, during final squeezing of the intraocular lens to force the still exposed trailing haptic inwardly of the corneal incision, the transverse edge portion thereof, especially where formed as a limb extending from a base stem situated on the optic peripheral edge, must be carefully negotiated through the incision in awkward, yet delicate, manner.
In this regard, the trailing haptic transverse length is as long as the incision when the "lips" of the incision are closed, yet it still extends outwardly of the eyeball and requires a spreading of the lips of the incision for insertion thereof. Such spreading, however, results in a shortening of the incision, thereby making the task of insertion even more difficult. Hence, while the leading haptic can be readily "snaked" through the incision, such "snaking" is not possible for the trailing haptic.
Since the typical length of the haptic transverse edge portions is about 6 mm and that of the incision is about 6 mm, when squeezing the known intraocular lens to force the last part of the trailing haptic inwardly of the incision, little tolerance exists between the incision and trailing haptic transverse edge portion, and this intensifies the danger of accidental twisting of the optic and possible injury to the closely disposed natural lens.
U.S. Pat. No. 4,174,543, issued Nov. 20, 1979, to Kelman discloses an intraocular lens having a small size optic, and a pair of generally diametrically opposed deflectable position fixation haptics extending outwardly therefrom, each provided with an outer transverse edge portion having a pair of laterally spaced apart contact lobes or the like for four point fixation in the eyeball, e.g. at generally diametrically opposed pairs of tissue points in the angle groove, upon insertion of the intraocular lens through a corneal incision.
Although the known type intraocular lens of this patent can be implanted as a corrective lens for use with an intact natural lens, it is primarily taught as a replacement for the natural lens upon extracapsular removal of the latter, e.g. to correct a condition such as aphakia, after removal of a cataracted natural lens. In the case where the natural lens is surgically removed, there is no danger of injury thereto when the intraocular lens is inserted through the incision into the eye.
Hence, in use of the intraocular lens of this patent as a replacement for the removed natural lens, the length of the common size and shape leading and trailing haptic transverse edge portions which contain the laterally spaced apart pairs of contact lobes or the like is not critical. In practice, as earlier noted, this length is about 6 mm to afford relatively maximum stability of lens fixation by providing correspondingly thereon similarly spaced apart contact lobes, while the overall longitudinal length from one such pair of contact lobes to the opposing pair, i.e. in undeformed or relaxed condition, is about 13 mm for accommodation in the approximately 12.5 mm diameter angle groove of the eye.
In such case, although the intraocular lens of this patent is squeezed in order to insert the exposed trailing haptic, the only risk is that accidental dislodgment of the already positioned leading haptic will require readjustment and repeating of the manipulation, with at most temporary trauma to any adjacent tissue that might be touched, but without any danger of injury to the natural lens, as the latter has already been removed per the contemplated procedure. On the other hand, where the intraocular lens of this patent is implanted as a corrective lens for an intact natural lens, the above noted problems and dangers regarding the natural lens are directly encountered.
U.S. Pat. No. 4,253,200, issued Mar. 3, 1981 to Kelman shows an intraocular lens having an optic provided with a pair of diametrically opposed haptics, one of which is longer than the other in radial distance as measured between the optical axis of the optic and the outer end of the haptic. These haptics do not contain spaced apart pairs of opposing contact lobes for four point fixation. Instead, the intraocular lens is used as a replacement for a natural eye lens, upon extracapsular removal of the latter, such that the radially longer haptic is positioned in linear contact with the ciliary sulcus and the radially shorter haptic is positioned in linear contact with the capsular bag from which the natural lens has been removed.
It would be desirable to provide a corrective intraocular lens for implantation in an eye, for use with an intact natural eye lens, permitting efficient insertion of the intraocular lens through a minimum size corneal incision, e.g. of length corresponding substantially to the diameter of the optic of the intraocular lens, especially in the case of an anterior chamber for correcting high myopia eyes, with minimum danger to the patient from accidental touching of the natural lens during the insertion procedure, and at the same time provide for adequate stability of fixation of the intraocular lens once implanted.